Autoimmune Disorder Left Ashton Kutcher Unable to See, Hear, or Walk

In tonight's episode of National Geographic's Running Wild with Bear Grylls: The Challenge, Ashton Kutcher opens up about a rare autoimmune disorder that left him temporarily unable to see, hear, or walk.

In a sneak peek of the episode obtained by Access Hollywood, Kutcher speaks about being diagnosed with a rare form of vasculitis. Vasculitis is an autoimmune disorder that has many variations and can cause inflammation of the blood vessels. This restricts blood flow and can even lead to organ and tissue damage.

"Like two years ago, I had this weird, super rare form of vasculitis, that like knocked out my vision, it knocked out my hearing, it knocked out like all my equilibrium,” Kutcher says to Bear Grylls. "It took me like a year to like build it all back up."

Kutcher adds, "You don't really appreciate it until it's gone — until you go, 'I don't know if I'm ever gonna be able to see again. I don't know if I'm ever gonna be able to hear again. I don't know if I'm ever gonna be able to walk again.'"

"The minute you start seeing your obstacles as things that are made for you, to give you what you need, then life starts to get fun, right?" Kutcher continues. "You start surfing on top of your problems instead of living underneath them."

Ashton Kutcher's episode of Running Wild with Bear Grylls: The Challenge airs Monday night at 9:00 PM ET on National Geographic.

Deena ElGenaidi's writing has been featured in Nylon, MTV News, Insider, The AV Club, and more. You can follow her on Twitter @deenaelg.